How to Georeference an Image or a Scanned Map using ArcMap

hello everyone welcome to this obvious tutorial on how to georeference an image or a scan map I have divided this tutorial into two parts in the first part I'll show you how to georeference an image without any information without any coordinate information stated on the figure for example for this tutor I have selected this figure which is a map a scan map of Belgium and if i zoom in you can actually see that we don't have any coordinate information stated on the map instead we just see some few names of the major cities so in part one I will be showing you how to georeference this image with absolutely no information on the coordinates and in the second but I have another picture actually it's the same picture but with some coordinate information for example you can see here if i zoom in a little bit mmm you can see that we have around one two three four five we have five random points where we actually have the the latitude and longitude coordinate information so I'm going to actually utilize this information in the second part of the tutorial too to do a more precise geo referencing so let's go ahead and get started with the tutorial all right now we have open arcmap already first of all the first step that we need to do is to make sure that we are in the correct coordinate system which means if we haven't defined any coordinate system we have to go to layers right click and go to properties and from here you have to select your desired coordinate system now for this tutorial I'm going to go with the web Mercator coordinate system so it's it's a projected coordinate system and as you can see I'm going to use the 1984 WGS web market auxilary sphere coordinate system I supply and then okay next we need to include those maps that I showed you before in the presentation into our art map interface so so in order to do that you need to first go to a log and navigate to the to the folder where you you have saved those images now here as you can see under the Belgium folder I have got two images so the first image is actually for the first part of the tutorial and second image is for the second part of the tutorial so for now I'm going to go with the Belgium image I'm going to drag I'm going to simply drag and drop this image into our arcmap interface press yes and as you can see we are getting a warning from RJ saying that unknown spatial reference now this is to be expected because this image is not geo-reference which means arcmap really does not know where where exactly to place this map which means this map does not carry its own projection yet alright now as you can see we have successfully added the map which does not contain any coordinate information now the next thing is to actually add a shape file which we could use as a base as a reference now in this in this case for this tutorial I have prepared a shape file which is a polygon which covers the area of Belgium so that's actually the map that I'm going to use as the reference map when you are referencing this image so let's go to catalog again and I have that file that shape file which is called Belgium and I'm going to just drag it and drop it on top of this map now as you can see nothing happened actually it's not that nothing happened we already added this Belgium shapefile but it's just not visible to us because it got placed somewhere else let's do to the fact that this Belgium shapefile does contain the correct projection if I go here and right click and then go to properties and if I go to source you can see actually the geographic coordinate system is WGS 1984 so that means it has its own projection already so if I go here and then if I go to the zoom to layer we can see we already have the shapefile over here which is not exactly the same place where we where we placed the image now what we need to do is somehow get that image to fit into this this window so how do we do that we need to use this geo referencing in order to do that now in case if you cannot see this you're referencing panel in your in your ArcGIS interface but you can simply do is you can simply right-click over here and go to 0 referencing just like that you can activate it so after you activate that you can go to this panel and make sure that you have selected your image whatever the image it could be it could be a JPEG it could be a gif it could be a PNG whatever the image is you need to make sure that you have selected that image over here after that you can simply go to georeferencing and you can click fit to display so now you can see that the map which was placed initially somewhere else now got moved into the same window which makes things quite easier for us also I'm going to actually change the color of this of this shapefile actually I'm going to make it colorless the fill color I'm going to assign as no color and just I'm going to leave the outline color and then make the the border a little bit more thicker so that we can actually see what we are dealing with and we can actually clearly see the the map which is located behind the shape file since we do not have any coordinate information content in the map at this moment the only way that we could retiro reference this map is just by moving the moving the map which is located behind the shapefile and trying to end by trying to adjust the the the shape and the size of the map so what I'm going to do first is as you can see here our our scan map looks a little bit smaller than the now as you can see we have the the country boundary of Belgium over here which is which is in red color and we also have the boundary of Belgium in the scan map which is marked in yellow and black color the way that I'm going to actually geo reference this image is by moving this image by resizing it and by shifting the image accordingly to match the to match the boundary of the scan map to the boundary of the shapefile that's basically our only option at this moment since we do not have any coordinate information so let's go to this option and we can see we have the option we have the option to rescale the map after I click scale now as we can see the the scan map looks a little bit smaller than the the shapefile so I'm just going to increase the size of the of the scan map a little bit more all right now let's let's let's draw attention to this this region I'm just trying to somehow match this line to be on top of this line so in order to do that I have to go to here again and use shift and I will shift the map slightly until it fits this boundary now if you look over here you can see actually it's perfectly overlapping each other but when you see over here you can see that it's things are not really correct over here so what I'm going to do is I'm I'm going to actually a rescale the map scale it up a little bit more just a bit more all right now I'll shift the map again this time shifted downwards all right now you see over here in the northern part of the country it's quite precise but over here we see that still we have some some areas where it's not perfectly overlapping so if I want to be a little bit more precise what I could do is I could actually scale down the map a little bit and shift it again over here all right I think you might agree that now it looks much much better than the previous one so after you have done this you can now clearly see actually the the red color boundaries perfectly overlapping the the boundary of the of the scan map now after once you are done with this this means actually we have correctly geo-referenced our map but just before we proceed to the second part of the tutorial I would like to show you something once you are done with geo referencing this image you need to go to geo referencing and you have to update the geo referencing now what happens when you do that if you go to that place where you saved your file again you will see that we now have three new files which got added actually these files contain the geo reference information so if you need to move this image to a new location you have to make sure that you move all these four files together as a pack so that it will actually recognize its its geographic location as well now in case if you happen to move this file alone that means this file does not contain the geo-referenced information anymore which will require you to georeference the file again after you update the geo referencing you can just simply close this file and if you were to drag that file and drop it again you see that it's getting station in the in the correct location unlike the previous time all right now let's move into the second part of the tutorial where we deal with an image which core which contains coordinate information which will enable us to do a more precise dereferencing compared to this one I'm going to repeat the same steps that we did in the previous part just going to catalog and now this time I'm going to select the Belgium to image press yes and this is something to be expected after that I'm going to add the shapefile again alright as expected the shapefile got placed somewhere else and I'm going to navigate to the shapefile through zoom to layer option and I'm going to make this transparent and only leave the boundary of the other shapefile I will make sure that I have selected Belgium to image over here and go to Jo referencing and click fit to display so before using this coordinate information I would like to just first of all do a rough rescaling of the map so that we can be sure that we are not like way off as long as you can see visually that the map map is not in place you can still actually play around with these tools but now instead of relying on these tools completely what I'm going to do is I'm going to actually rely on on some of these coordinate information that we have now as we can see here this pinpointed location should actually be roughly moved to this this edge of the shape file so what I'm going to do is I'm going to go to add control points and I'm going to click here first I will click on the location on the on the scan map and right click and click on add DMS here DMS stands for degrees minutes and seconds so here we have the degree I'm going to actually include this information over here we have two degrees thirty two minutes and forty five point nine eight one seconds and this is east and the latitude it's fifty one five and twenty three point two five two note click OK and as you can see that point got moved to somewhere over here now if you have another corner like that for example this corner you know that this corner needs actually to be placed over here so I'm also going to actually correct this corner as well since I have the coordinate information over I will click somewhere over here right-click and input DMS of lat/long now my degrees is three I will zoom this out a little bit three degrees twenty two minutes eleven point nine eight one seconds and the latitude is 51 degrees twenty two minutes and zero point three one one seconds all right as you can see that point also got moved over here as we expected now what else we can do all right as we can see the generally image got rescaled quite successfully but if you go to some edges here over over here in the South you still see that actually there is a slight shift so what you can do here is you're good you select add control points again and this time we don't have any coordinate information so what you can do is you can add two control points one is over here in the scan map and you can actually push this point to be at this point by selecting this point next now you can see actually it got moved this we actually need a proper distribution of control points through the map so maybe I will go to some region in the north this looks quite oaky to me so I think I will just try to find a place in the from the South yeah maybe this point and I'm going to select the point of the scan map and try to shift it to be right underneath the shapefile like so all right as you can see we have generally done done a good job but I'm not going to actually spend much more time in perfecting the geo referencing but I think you guys got the basic idea of how to perform an geo referencing in a case where we don't have any information and for a case where we have some coordinate information again make sure that you have done the update geo referencing again otherwise your image will not be geo reference properly so just for the demonstration purposes I'm going to remove this image again let's go to catalog and try to drag and drop that image and as you can see everything works perfectly fine so that's pretty much it for today's tutorial I hope you enjoyed this tutorial and if you did it thumbs up and if you would like to see more tutorials on the practical use of ArcGIS and also a Python programming you could also consider subscribing thank you and have a good day

Channel: GeoDelta Labs

Views: 50,244

Rating: 4.9225807 out of 5

Keywords: Georeference, Scanned map, How to, ArcMap, ArcGIS, Projection, Maps, Cartography

Id: _W_wN0gZJl0

Length: 17min 9sec (1029 seconds)

Published: Sun Nov 11 2018